Executives at the Ann & Robert H. Lurie Children's Hospital of Chicago expected a "bump" in patients when the $855 million hospital opened in June.

They weren't prepared for a mountain.

Since the former Children's Memorial traded its patchwork of aging buildings in Lincoln Park for a new high-rise in Streeterville on June 9, patient volume has surged, more than doubling hospital projections.

The number of patients is up about 16 percent in the first five months, according to hospital data, an increase driven by an influx of children with more acute health problems, including transplant patients, kids with heart problems and others in need of specialized care.

Revenue over that five-month period increased 12.9 percent to $222 million.

"We expected to have a new-hospital bump in (patients). We had a new-hospital mountain," said Michelle Stephenson, Lurie Children's chief patient care services officer and chief nurse executive. "We've had some months where the (number of inpatients) was 24 percent over what we expected. "

To meet the demand, the hospital hired 151 nurses to ensure full coverage, she said.

Those new hires came on top of about three dozen pediatric specialists and department heads Lurie Children's recruited in the run-up to the hospital opening.

Stephenson said the hospital has yet to determine the specific reasons behind the jump in patients, but said data shows it is drawing more children from the collar counties and downstate.

She also cited the location, adjacent to Northwestern Memorial Hospital, Northwestern University's Feinberg School of Medicine and Prentice Women's Hospital, which is connected to Lurie via an enclosed skyway.

Moving 31/2 miles south next to Prentice, which sends Lurie about a quarter of its patients, is likely a significant factor in the patient boom, said Jay Warden, a senior vice president at The Camden Group, a consulting firm.

"It used to be a challenge for moms to have a baby transferred to Children's while they had to stay at Prentice until they're discharged," Warden said. "Now it's the best of both worlds for both hospitals."

Warden said hospitals typically get a burst of new patients when they open facilities, in part because of the accompanying marketing and publicity blitz. That's not always the case with children's hospitals, which tend to serve the sickest and smallest of patients who have few other options.

He said limitations at the old hospital likely kept some patients away.

Indeed, Children's Memorial had a listed capacity of 247 beds, but with shared rooms and other factors, executives considered the hospital full at 220 patients, Stephenson said. The Lurie hospital has a capacity of 288 beds in all-private rooms, which it has come close to filling on a few occasions.

One ward that's consistently bursting at the seams is the neonatal intensive care unit, which was built to handle 44 patients but is averaging about 50. Some of the children have been bumped into shared space in the hospital's cardiac care unit, Stephenson said.

As for patients, the new facility has been a hit, with satisfaction scores up an average of 10 percent, hospital officials said.

Tina Sneed, whose 18-year-old daughter Whitney Ballard recently underwent a liver transplant at the hospital, said she's happy with the expanded rooms and new areas for parents.

She and her daughter have made several 7-hour trips from Kentucky in the last 18 months to see specialists, including overnight stays at both facilities.

Her only complaint?

"The waiting room was kind of crowded," she said. "It was nothing too bad, they just have so many (surgeries) going on at the same time we barely had room to move in there."